Method of detonating ammonium nitrate base explosives



Fume 3G, 1959 J. R. HHADEL, H AL Z@ METHOD OF' DETONATNG AMMONIUM NITRATE BASE EXPLUSIVES Filed July 50, 1956 RHI.

.loseph R. lllrndel, Mount llt, Mich., and Harold E. Stantlt and Parke D. Muir, luisa, Okla., assigner-s to The Dow Chemical Company, Midland, Mich., a corporation ot Delaware applicaties my su, 19st, seam N0. masas l (ci. 1oz-23) into the well bore, forcing the slurry into oil or gas bearing formations, and then detonating the explodable components of the slurry by means of shaped charges which produce Munroe jet type explosions.

The shaped charges are commonly detonated either by means of a time delay type detouator or the detonation is initiated through electrical cable means which is coupled to a suitable control unit disposed near the well head.

The arming of the shaped charge detonating devices at the well head constitutes a safety hazard which can be minimized by good explosives handling technique but which cannot be entirely overcome.

Also, if the explosive detonating devices fail to fire in the well bore, their removal from the well is hazardous.

ln addition, shaped charges, in order to insure the most extensive explosion of the ammonium nitrate, should either be disposed in a slurry of ammonium nitrate or have the jets directed into the slurry when the shaped charges are detonated. When the slurry is mainly disposed in fissures communicating with a well bore wall, it is often difiicult to accurately dispose the shaped charges so as to direct the explosive jets into the slurry.

Accordingly, a principal object of this invention is to provide a safer, more elective method of exploding ammonium nitrate in an earth well.

In accordance with this invention a slurry of ammonium nitrate is pumped into an earth well, a container of Thermit-type explosion initiation material is disposed in the well in communication with the slurry, the slurry and explosion initiating material are placed under pressure, and the Therrnibtype explosion initiating material is ignited. The high temperatures and increased gas pressure resulting from the burning of the Thermit detonate the explodable elements in the slurry.

The invention, as well as additional objects and advantages thereof, will best be understood when the following detailed description is read in connection with the accompanying drawing. The drawing shows, in diagram-4 matical form. a well bore having ammonium nitrate slurry therein and an explosion initiating device of the Thermit type communicating with the slurry, the well being under pressure.

Referring to the drawing, there is shown a well bore, indicated generally by the numeral 10, which extends from the surface 12 of the earth through a number of earth formations i4, 16 and an oil bearing formation lll. A string of casing 20 extends into the well bore lll and is bonded to the well bore wall 22 by cement 24. The upper and of the casing 2d terminates in a header, indicated generally by the numeral 26, to the top ot which is atlaten'led ,lune 30, i959 tached a smiling bon 2li. Two sections of pipe, 3u, 32 are coupled to the header 2li. Valves 34, 36 are provided in the pipe sections 30, 32, respectively. A pres sure gauge 38 is coupled to the pipe 30 between the valve 34 and the header 2.6. A pump 40 is coupled to the pipe 30 on the side of the valve 34 which is remote from the header 26.

A cable 42 extends from a draw works ddl (driven by a suitable motor 46) over a sheave 48 suspended from a derriclr 5G, through the stuit'ing box 28, and down the well bore l0 to near the pay or oil producing formation l.

ln practicing this invention a pumpable slurry 5d comprising ammonium nitrate and a suitable liquid is pumped into the well bore lll and, usually, forced under pressure into fissures 52 in the producing formation 18. Some of the slurry may be left in the well bore itl as shown at 54. After the injection is made ammonium nitrate particles usually settle out oi the slurry, forming a more or less continuous train 5S of nitrate particles on the bottom of the lissures 52 and well bore lll. A Thermit type igniter-detonating device 56 is placed in the well bore adjacent to or in the slurry 5d or the settled ammonium nitrate particles thereof. The device 56 may either be lowered into the well bore lll on a cable 4Z, as illustrated, or may be dropped into the well bore l0. The igniterdetonating device 56 may be actuated electrically through electrical conductors of a cable (such as the cable 42, for example) to permit control of the detonation from the earths surface l2. Alternatively, the device S6 may be actuated by a suitable timing mechanism enclosed within the device 56. The device 56 may be disposed in the slurry 54 or just above the slurry so that molten combustion products from the device 56 may drop into the slurry 54, and reach ammonium nitrate particles 55.

A suitable ignitendetonating device 56 comprises a huid-tight container of a Thermit-type material, commonly aluminum and ferrie oxide (in the ratio of 3 mols of aluminum to 3 mols of ferrie oxide), plus igniting powder capable of being ignited by a hot wire, and an electrical squib which is connected to a control circuit (self contained o`rotherwise). However, other Thermit-type mixtures, such as a copper oxide and aluminum mixture, may be used in practicing this invention.

That part of the well bore l0 and ssures 52 in which the slurry 54 is disposed is placed under at least 300 pounds per square inch of pressure before detonation of the slurry 54 (or the explosive part of the shury S4) takes place. The pressure of 30G pounds per square inch may be induced by a fluid column, such as the column 58, or by closing the valves 34, 36 and stuing the box 28 to maintain the well bore lll under hydrostatic pressure. Alternatively, tamping 60 may be deposited in the lower end of the well bore 10 and the minimum pressure of 300 pounds per square inch induced by the rapid formation of gases as the Thermit and slurry burns after the igniterdetonating device 56 is actuated.

A combination of hydrostatic pressure on the slurry and tamping above the slurry may also be used to advantage. The tamping, in such applications, usually serves to somewhat limit the upward blast of the explosion of the slurry.

The Thermit, being ignited while the slurry 54 is under pressure as described above, rapidly burns with intense heat through the slurry 5ft, the heat and resultant pressure thus initiating the explosion of the explodable elements within the slurry.

The slurry 541 commonly comprises particulated ammonium nitrate mixed with enough petroleum, other oil. or Divers liquid to make the mixture iiowable. Three hundred to four hundred gallons of petroleum oil per ton of particulated material has been found to make a pumpable slurry.

senese One slurry which was detonated successfully in accordance with this invention contained prelled and tine particles of ammonium nitrate. The tine particles had the following sieve analysis:

Sieve: Percentage Through 10, retained on 20 7 Through 20, retained on 40 31.4 Through 40, retained on 60 13.0 Through 60, retained on 100 36.6 Through 100, retained on 200 12.0

The prelled particles of ammonium nitrate has the following sieve analysis:

Sieve: Percentage Through 6, retained on 22.9 Through l0, retained on 20 76.5 Through 20, retained on 40 0.6

The composition of the ammonium nitrate particles need in the above described slurry is: paraiiin 0.7 percent, diatomaceous earth 0.5 percent, the remainder being arnmonium nitrate.

We claim:

l. The method of initiating the explosion of explodable material in a slurry comprising ammonium nitrate as a major constituent thereof, comprising pumping said slurry into a well bore, depositing a Thermit type igniterderonator device adjacent to said slurry, igniting said igniter-detonator device and maintaining said slurry under pressure of at least three hundred pounds per square inch while said igniter-detonator device burns.

2. The method of treating a well having a bore which penetrates earth formations, comprising pumping a slurry which compris'es ammonium nitrate as a major constituent thereof into said bore, depositing a Thermit type igniterdetonator device in said bore above the lower level of said slurry, placing said slurry in said well bore under pressure of at least three hundred pounds per square inch, igniting said igniter-detonator device and dispersing moltert, combustion products thereof into said slurry.

3. The method of initiating the explosion of explodable material in a slurry comprising ammonium nitrate as a major constituent thereof, comprising pumping said slurry into a well bore, depositing a Thermit type igniter-detonator device adjacent to said slurry, depositing tamping material in said well bore above said slurry, igniting said igniter-detonator device and maintaining said slurry under pressure of at least three hundred pounds per square inch while said igniter-detonator device bums.

4. The method of treating a Well having a oore which penetrates earth formations, comprising pumping a slurry which comprises ammonium nitrate as a major constituent thereof and a petroleum oil into said bore, depositing a Thermit type igniter-detonator device in said bore above the lower level of said slurry, placing said slurry in said well bore under pressure of at least three hundred pounds per square inch, igniting said igniter-detonator device and dispersing molten combustion products thereof into said slurry.

5. The method of initiating the explosion of explodable material in a slurry containing ammonium nitrate as a major constituent thereof, comprising pumping said slurry into a well bore", depositing a Thermit type igniter-detonator device adjacent to said slurry, lling at least a part of said well bore with a liquid to maintain said slurry under pressure of at least three hundred pounds per square inch, and igniting said igniter-detonator device to disperse molten combustion materials through said slurry.

6. The method of treating a well having a bore which penetrates earth formations, comprising pumping a slurry which comprises ammonium nitrate and Divers liquid as the major constituents thereof into said bore, depositing a Thermit type igniter-detonator device in said bore above the lower level of said slurry, placing said slurry in said well bore under pressure of at least three hundred pounds per square inch, igniting said igniter-detonator device and dispersing molten combustion products thereof into said slurry.

7. The method of treating a well having a bore which penetrates earth formations, comprising pumping a slurry which comprises ammonium nitrate as a major constituent thereof, ammonia and water into said bore, depositing a Thermit type ignited-detonator device in said bore above the lower level of said slurry, placing said slurry in said well bore under pressure of at least three hundred pounds per square inch, igniting said igniter-detonator device and dispersing molten combustion products thereof into said slurry.

References Cited in the tile of this patent UNITED STATES PATENTS 1,104,011 Snelling July 21, 1914 2,246,611 Zandmer June 24, 1941 2,463,709 McFarland Mar. 8, 1949 2,708,876 Nowak May 24, 1955 

1. THE METHOD OF INITIATING THE EXPLOSION OF EXPLODABLE MATERIAL IN A SLURRY COMPRISING AMMONIUM NITRATE AS A MAJOR CONSTITUENT THEREOF, COMPRISING PUMPING SAID SLURRY INTO A WELL BORE, DEPOSITING A THERMIT TYPE IGNITERDETONATOR DEVICE ADJACENT TO SAID SLURRY, IGNITING SAID IGNITER-DETONATOR DEVICE AND MAINTAINING SAID SLURRY UNDER PRESSURE OF AT LEAST THREE HUNDRED POUNDS PER SQUARE INCH WHILE SAID AGNITER-DETONATORDEVICE BURNS. 